For decades, Miami has been a dominant force in the sandwich universe. Sure, New York and Chicago have claims, but the Magic City is one of few where the sandwich plays an integral part of life. Though Cuban sandwiches have long reigned supreme, a few years ago the intensely flavorful sandwiches of Peru appeared on the scene, and life has never been this same. The family-owned Mr. & Mrs. Bun in West Kendall specializes in what it calls panceta en caja china ($11.99). Pork belly is cooked in a special roasting box until the meat's absurdly tender fat and flesh are encased in a crisp crust. It's tucked inside a fluffy house-made bun with crisp sweet potato coins, crunchy lettuce, and a tangy mayonnaise. In Peru, these sandwiches are popular as drunk food, but there's no need for booze to make this version the best.